Retention of tritium in carbon co-deposits is a serious concern for ITER. Developing a reliable in-situ removal method of the co-deposited tritium would allow the use of carbon plasma-facing components which have proven reliable in high heat flux conditions and compatible with high performance plasmas. Thermal oxidation is a potential solution, capable of reaching even hidden locations. It is necessary to establish the least severe conditions to achieve adequate tritium recovery, minimizing damage and reconditioning time. The first step in this multi-machine project is 13C-tracer experiments in DIII-D, JET, C-Mod and MAST. 13CH4 is injected toroidally symmetrically, facilitating quantification and interpretation of the results. Tiles are then removed, analyzed for 13C content and subsequently evaluated in a thermal oxidation test facility with regard to the ability of different severities of oxidation exposure to remove the different types of (known and measured) 13C co-deposit. Removal of D/T from B on Mo tiles from C-Mod will also be tested. OEDGE interpretive code analysis of the 13C deposition patterns is used to generate the understanding needed to apply findings to ITER. First results are reported here for the 13C injection experiments in DIII-D.